Various secondary batteries such as a lithium ion secondary battery are employed as a secondary battery of a so-called electrically-driven vehicle such as an electric vehicle or a hybrid vehicle. Such a secondary battery is charged, for example, using a quick battery charger or the like.
For example, a charger for charging a secondary battery is discussed in JP 2013-192348 A, in which a chargeable power is calculated on the basis of a charging target voltage and a measurement voltage of the secondary battery, and control is performed such that the output of the charger reaches the chargeable power. In this charger, its output may become higher than the chargeable power, and the voltage of the secondary battery significantly exceeds the target voltage, for example, if an abnormal situation occurs in the charger. This may deteriorate the secondary battery.
In this regard, for example, as discussed in JP 2014-75256 A, in order to prevent the charging voltage from significantly exceeding the target voltage, it is conceived that the charging power charged to the secondary battery from the charger may be restricted to a sufficiently low value when the cell voltage becomes higher than the target voltage (for example, the charging current may be restricted to zero by electrically disconnecting the charger and the secondary battery).